A ladder is leaning against a wall. The top of the ladder is 999 feet (\text{ft})(ft)left parenthesis, f, t, right parenthesis above the ground. If the bottom of the ladder is moved 3\,\text{ft}3ft3, space, f, t farther from the wall, the ladder will be lying flat on the ground, still touching the wall. How long, in feet, is the ladder?